In 1932, the Type E coupler was adopted as the ARA, American Railway Association (predecessor to the AAR, Association of American Railroads) standard coupler for railway freight cars. Although modified periodically since then to meet changing requirements imposed by changing demands, and other coupler designs have been developed for special applications, the Type E coupler is today still the standard coupler for freight service. As the standard coupler, all producers of such couplers in the United States are required to produce the couplers to the standard specification, at least for use within the USA, so that such couplers are not only completely interchangeable, regardless of the manufacturer, but more importantly, so that the couplers from any manufacturer can readily be joined to couplers from any other domestic manufacturer.
The Type E coupler is well known to those knowledgeable in the trade as having a pivotal, vertical-knuckle adapted to engage an identical vertical-knuckle on an adjacent coupler, so that when the couplers are brought into contact with each other, the two knuckles are pivoted into an interlocking, engaging position. Each coupler includes a gravity activated coupler lock member adapted to slide downwardly after coupler engagement to virtually lock each knuckle at it's engaged position. To permit the coupler to become disengaged, each coupler lock member must be raised within its slide-channel, so that a draft load on the couplers tending to pull the cars apart, will cause the knuckles to pivot away from each other, thereby becoming disengaged.
The Type E railway coupler further includes a cast steel coupler head at the forward end extending from a shank which is fitted within and attached to a yoke, which secures the shank end of the coupler to the railway car. The forward end of the coupler head is generally V-shaped in horizontal cross-section with the "V" opening facing outwardly from an end of the railway car with the above-described vertical-knuckle pinned at one side to form one leg of the "V". The other leg of the "V" comprises a fixed and rigid gathering arm, specifically, a forwardly extending head portion extending at an angle to the coupler center line and having an angled, inside gathering surface against which the vertical-knuckle on a mating coupler is intended to impact and be pivoted inwardly to a degree sufficient: to activate the lock and thereby be locked in place. Therefore, as a pair of such railway cars, and particularly a pair of such couplers, are brought together for coupling them together, the two opposed vertical-knuckles will contact the angled gathering surface on the adjacent coupler's gathering arm and be pivoted inwardly behind each other, thereby engaging each other and locking the two couplers together, as above-described. These and other operating parts of the Type E railway coupler are well known to those familiar with the art and have been since 1932, so that a further detailed description is not believed to be necessary here.
To permit a railway train to safely negotiate curves in the tracks, the coupler shanks are pivotally secured to the railway car, so that pursuant to AAR specification, each coupler shank can pivot 13.degree. in a horizontal plan to either side of the longitudinal center line of the railway car. Therefore, to readily join a pair of freight railroad cars together, it may be necessary to pivot the coupler shanks so that the coupler heads are generally aligned and directly opposed from each other. While proper straight alignment may naturally result when a pair of cars are disjoined while on a length of straight track, there are times, however, when they are not properly aligned for joining. For example, when a pair of cars are disjoined while oil a curved track the couplers will not normally extend perpendicularly from the end of the railway car. In addition, there are times when railway cars to be joined are on a length of curved track, and hence the coupler shanks are preferably not oriented perpendicularly from the ends of the car to be joined. Accordingly, it may be necessary for an operator or trainman to manually position the coupler or couplers by pushing or pulling it or them into proper alignment before the cars can successfully be joined together by moving one into the other. If attempts to join a pair of railway cars are made when the couplings are not properly aligned, the impact of misaligned couplers may cause damage to one or both couplers.